Chair base



FIG. 1 is a perspective view of a chair base incorporating the design of the present invention.

FIG. 2 is a top view of the chair base.

FIG. 3 is a side view of the chair base positioned such that one of the legs of the base is in the center of the view.

FIG. 4 is a side view of the chair base, slightly rotated from the position shown in FIG. 3 positioned such that the center of the view is between two legs of the base; and,

FIG. 5 is a bottom view of the chair base. 

The ornamental design for a chair base, as shown and described. 